Magnetron anode structure



P 22, 1953 E. EVERHART 2,653,275

MAGNETRON ANODE STRUCTURE Filed June 1, 1945 INVENTOR EDGAR EVERHART ATTORNEY Patented Sept. 22, 1953 UNlTED STATES PATENT DFFICE MAGNETRON ANODE STRUCTURE Edgar Everhart, Cambridge, Mass., assignor, by mesne assignments, to the United States of America as represented by the Secretary of War Application June 1, 1945, Serial No. 597,032

2 Claims.

My invention relates in generalto electrical apparatus and more particularly to improvements in magnetron oscillator tubes.

Conventional present day magnetrons consist of a plurality of elementary resonators symmetrically positioned in an anode block surrounding a cathode. Electrons emitted from the cathode are brought into oscillation while passing from the cathode to the anode and set up oscillation in each of the elementary resonators. Oscillation can occur in any one of several modes, one of which in general will be more efiicient than the others, thus rendering it more desirable.

The separation in wavelength of the possible modes of oscillation is largely determined by the amount of coupling between the elementary resonators. When two modes occur at almost the same wavelength the excitation of one may bring the other into oscillation with a resulting loss in efficiency. Generation of two such modes may be avoided by a technique known in the art as strapping.

In its simplest form, strapping consists of connecting a short length of conductor between two anode segments which are separated by a single segment. It has been found that the inductance of the conductor together with the capacity between the conductor and the intervening anode segment will afford increased coupling between the strapped circuits. There are numerous forms and types of straps which may differ from one another slightly in their electrical characteristics but which are in general merely extensions of the elementary type of strap described above.

It is desirable to have as large a power output from a magnetron oscillator as is possible. One method of increasing the output of such an oscillator is to increase the length of the cathode, and with it the anode, thus providing higher currents due to the increased cathode emitting surface. A difficulty encountered in this practice is that increasing the length of a-magnetron while employing straps only at the ends of the anode permits variations in the electromagnetic field along the cathode and small areas of the cathode may be submitted to an undesirably high electron back bombardment or to current density requirements higher than that for which the cathode emitting surface is designed.

Accordingly, it is one object of my invention to provide means for separating nearby oscillatory modes in a magnetron oscillator.

Another object is to provide a magnetron tube with increased power output.

Still another object is to reduce the possibility of damage to the cathode emitting surface in a magnetron tube.

The invention will best be understood with reference to the following specification, claims and drawings in which:

Fig. 1 is a perspective view of a cross-section of a magnetron tube employing one embodiment of my invention; and

Fig. 2 is an end view of the magnetron tube shown in Fig. 1.

Briefly, the invention may be likened to a magnetron wherein two conventional anode blocks which are end strapped are placed one over the other and used in conjunction with a single elongated cathode. Thus, high current and hence high power output are gained from the increased cathode emitting surface. The presence of straps in the center of the magnetron anode prevents electromagnetic field variations along the length of the cathode. Referring now to Fig. 1, one-half of each of anode blocks 5 and t is shown. Cylindrical holes I are drilled through blocks 5 and 6 to form cavity resonators. These elementary resonators are joined to the central cathode-containing volume 8 by openings 9 which extend the length of the two anode blocks. Thus, segments H are formed in blocks 5 and 6.

Generally, the magnetron is designed to oscillate in a mode which causes adjacent segments to be of opposite polarity at any given instant, variations in voltage on adjacent segments being out of phase. Strapping is accomplished by connecting alternate segments by thin strips or wires i3, H5, I5, and it of conducting mate-.

rial. In the magnetron of Fig. 1, straps l3 and is are mounted flush with the outer faces of blocks 5 and 6, wider grooves being cut in those segments with which it is desired that the straps do not make contact, and straps i4 and I5 are recessed more deeply into the inner faces of blocks 5 and 6 to prevent electrical contact and short circuiting between the two straps.

Fig. 2 shows in its entirety the upper face of anode block 5 in which the symmetrical arrangement of resonators i can be seen as well as the complete form of strap IS. The latter is a complete ring of conducting material concentric with anode block 5. In addition, cathode I8 is shown in proper relation to the other components of the magnetron.

It will be understood that what has been described herein is a preferred embodiment of my invention and deviations therefrom may be made without loss of the advantages thereof. Hence, I claim all such modification and adaptations as fall within the spirit and scope of the hereinafter appended claims.

What I claim is:

1. A magnetron having an anode electrode and a cathode electrode, said anode electrode comprising two similar substantially cylindrical blocks of conducting material juxtaposed with a plane face of one of said blocks in electrical contact with a plane face of the other of said blocks, said anode blocks being chambered pen pendicularly to said plane faces of said blocks, forming a coaxial chamber and a plurality ofcavity resonators positioned symmetrically around said coaxial chamber, said cavity resonators connected to said coaxial chamber by axial slots thus segmenting the inner portion of said anode blocks, means electrically connecting alternate segments, said means comprising ringlike members of conducting material positioned substantially within the plane faces of said anode blocks, said segments completely inclosing said rings intermediate said coaxial chamber and said cavity resonators, the ring-like member positioned in one face of each of said blocks making electrical contact with one-half of said segments and the ring-like member positioned in the other face of the same block making contact with the remainingsegments, whereby the likelihood of simultaneous oscillation in two or more modes of oscillation and undesirable variations in the electromagnetic field along the cathode is decreased.

2. A magnetron having a cathode and an anode. said anode comprising; a plurality of cylindrical blocks of conductive material termiminating in plane faces perpendicular to the axis of said cylindrical block, an inner cylindrical chamber formed in each of said cylindrical blocks, coaxial thereto; outer cylindrical chambers equi-spaced about said inner chamber, equidistant therefrom and connected thereto by radial slots, said chambers and said slots extending axially through said cylindrical blocks; metallic rings positioned within each plane face of said cylindrical blocks, sections of said cylindrical blocks between adjacent slots completely enclosing said rings intermediate said inner and outer chambers, said rings engaging alternate sections between said slots, the remaining sections between said slots being recessed to avoid said rings, said. cylindrical blocks positioned with said alternate sections of one plane face engaging said other sections of th contacting plane face of the adjoining cylindrical block.

EDGAR EVERHART.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,187,149 Fritz Jan. 16, 1940 2,406,277 Bondley Aug. 20, 1946 2,414,085 Hartman Jan. 14, 1947 2,417,789 Spencer Mar. 18, 1947 2,432,827 Spencer Dec. 16, 1947 2,509,419 Brown May 30, 1950 2,542,899 Brown Feb. 20, 1951 FOREIGN PATENTS Number Country Date 445,084 Great Britain Apr. 2, 1936 

